Boards just disappeared from screen

We a group are working in a project using Jira, all of us have developer administrator access and all of us can see the board or the active sprints. All of a sudden, from one day to another, the button that allows us to see the active sprint borad has disappeared and only the leader can see it now. There is no known way to take it back, before all of the members of the group were able to see it and modify tasks.